More than anything I think it's a more tangible argument for how microtargeting can go south. Most people are ok with the concept of advertising in general, and microtargeting feels like a small step from normal ads. "Yeah I get it, people want to sell me shit, what's the big deal?" This is the big deal.

Advertising's purpose is to infect your mind and trick it into thinking what the ad-buyer wants. In the past it wasn't as big of a deal, advertisers are less likely to use direct lies or manipulations if the audience is big: they can get backlash, some tricks have the opposite effect on some people, etc. Now that they can target individuals every trick in the book is fair game.

Now, if you talk to someone about these problems, they'll usually say something like "oh well it might affect other people, but ads don't affect me." Or "why would they care that much about me?" Guess what, if a politician can be be targeted and manipulated, a disgruntled coworker can target you, your ex can target you.